1. Field of the Invention
The present invention relates to a buckle having three-way strap and used for securing a human body and the like.
2. Description of the Related Art
Conventionally, a buckle mounted to each coupling end portion of a three-way strap comprises a pair of plugs and a socket into which the pair of plugs are inserted and engaged with. An operating portion for resiliently deforming the engaged buckle to disengagement is mounted to the socket. For example, a buckle disclosed in Japanese Patent Application Laid-open Publication No. 7-246106 has a hinge portion which is a resilient portion formed integrally with an upper face of the socket, and a lock canceling button which is an operating portion is defined at a tip end of the hinge portion in a cantilevered state. A through hole is defined on a bottom face of the socket and corresponds to a position of the lock canceling button.
In a buckle disclosed in Japanese Patent Application Laid-open Publication No. 8-140712 of the same applicant as that of the present invention, a resilient portion is mounted from an inner side of a bottom face of a socket to extend diagonally toward an upper face of the socket in a cantilevered state, and an operating portion is mounted to a tip end of the resilient portion.
There is also a coupling device disclosed in Japanese Patent Application Laid-open Publication No. 8-89314, wherein a lock member which is an operating portion is separated from a socket. In this device, two resilient leg portions projecting diagonally and downward are formed at a bottom face of the lock member to abut on an inner side face of a bottom face of the socket, and the lock member is supported for projecting and sinking movements.
An operation of the buckle disclosed in each the above Japanese patent application laid-open publication is reliably carried out by inserting the plugs into inserting holes of the socket and pushing the plugs against a resilient force generated at the engagement. In order to pull the plugs out of the socket, the operating portion such as a lock canceling button of the socket is pushed. Thus, the engagements between engaged portions of the plugs and the socket are disengaged, thereby the pair of plugs can be pulled out of the socket.
In the case of the technique disclosed in above Japanese Patent Application Laid-open Publication No. 7-246106, because the through hole is defined on the rear face of the socket and which corresponds to the position of the lock canceling button, clothes or a finger may be caught on the lock canceling button, and the buckle is inconvenient to use. The lock canceling button is not sufficiently strong due to its cantilevered structure. Also, clothes or other members may be inserted and caught in the through hole which corresponds to the position of the lock canceling button, and thus, the lock canceling button may be stripped off and broken. In the case of the technique disclosed in Japanese Patent Application Laid-open Publication No. 8-140712, by pushing the operating chip of the operating portion, the pair of plugs are disengaged and the plugs jump out of the socket. Because the operating chip is supported by a resilient portion in a cantilevered state, displacement of the operating chip opposite to the resilient portion is liable to increase. Therefore, due to an operation of the operating chip, the plug inserted to an opposite side to the resilient portion is liable to be disengaged faster. As a result, there were differences in amounts of jumping out of the plugs and feelings at the time of the disengagement. In addition, the operating chip is not sufficiently strong due to its cantilevered state, and the operating chip may be stripped off similarly to the above Japanese patent application laid-open publication. In the technique disclosed in Japanese Patent Application Laid-open Publication No. 8-89314, both sides of the lock member can be evenly displaced by a pair of resilient leg portions. However, the lock member is formed independently, thereby increasing a number of parts and complicating the structure.